Data Sources: A search for studies published in peer-reviewed journals from 2005 to 2011 was conducted using MEDLINE, Agency for Healthcare Research and Quality Clinical Guidelines and Evidence Reports, and the Cochrane Database of Systematic Reviews. Related citations and expert recommendations were included.

Data Extraction: Studies were selected if the search terms opioid and the organ system of interest were in the article’s title, abstract, or text. Systems considered were gastrointestinal, respiratory, cardiovascular, central nervous, musculoskeletal, endocrine, and immune. Of 1,974 initially reviewed articles, 74 were selected for evidence regarding effects of chronic opioid use on that organ system. Of these articles, 43 were included on the basis of direct relevance to opioid prescriptions in the primary care setting.

Data Synthesis: A qualitative review was performed because the number of articles pertaining to specific adverse effects of opioids was typically small, and the diversity of adverse effects across systems precluded a quantitative analysis.